1. Field of the Invention
The present invention relates to a dual voltage switching circuit for a computer.
2. Description of the Related Art
In general, a computer can be configured by a user to enter a sleep mode to protect the computer and save energy by setting the advanced configuration and power interface (ACPI). The user can wake up the computer from sleep mode, by pressing a key on the keyboard, or by moving or pressing the keys on the mouse.
A working voltage is provided by a dual voltage switching circuit. When the computer is in a work mode, the dual voltage switching circuit provides a 5V system voltage. When the computer is in the sleep mode, the dual voltage switching circuit provides a 5V standby (5V_SB) voltage. The 5V_SB voltage is received by a power-on terminal of the computer via a transistor. When the power-on terminal receives a low voltage signal, the computer is powered on. However, power is also provided to peripheral equipments of the computer via the transistor. The transistor may be damaged by an overload current when too many peripheral devices, such as keyboards, mice, and USB devices, are connected to the computer at once. Therefore, the power-on terminal is unable to power up the computer due to the damaged transistor.
What is needed, therefore, is a dual voltage switching circuit to over come the above-described shortcoming.